UI_ShowClockPage()/UI_ShowSetTimePage() now take weekday/day/month(/year)
and build the date bar dynamically via Build_DateString() instead of
the fixed placeholder string. app_home.c reads the full date from RTC
via PCF8563_ReadDateTime() and recalculates weekday since the RTC's
stored date may differ from the software clock's. config.h exposes
current_day/month/year/weekday alongside the existing time fields so
main.c's debug commands don't need a separate include.